Earth boring machines that are used to create a horizontal bore, the bore being lined with a pipe casing, are well known in the art. Earth boring machines of this type typically utilize an auger at the forward, or leading, end of the pipe casing. The auger is rotated, thereby boring a horizontally disposed hole through the earth, the auger also carrying the dirt outwardly for disposal at rearward-most portion of the boring machine. Also at the boring machine, hydraulic pistons are used to drive the pipe casings through the bore as it is formed. Successive pipe casings are then attached to the series of end-to-end pipe casings as the bore progresses. In this fashion, a continuous bore and casing is made as desired or required for the particular application.
In order to achieve a final bore that is on grade, however, a steering head is typically located at the forward-most pipe casing or portion thereof. The steering head can be provided with a directional control device. This is also known in the art. One such control device is disclosed in U.S. Pat. No. 4,977,967 issued to Alston et al. In that type of device, a casing extension is pivotally attached to one end of a casing section and is controlled by an elongate tube that is movable along an axis that is generally parallel to the axis of the casing in order to pivot the casing extension upwardly or downwardly. A first connector for connecting one end of the tube to the casing extension and a second connector assembly connected to the other end of the tube for moving the tube and pivoting the casing extension is provided.
In the experience of this inventor, one difficulty encountered with the utilization of a steering head as described above is that a reversal of the steering head during the boring process tends to deposit earth into the drive mechanism, which is a threaded screw mechanism. The presence of earthen debris about the drive mechanism can cause the mechanism to seize when the boring head is re-activated to move forwardly. When this happens, the steering head mechanism will be inoperative, bring the boring process to a halt until the steering head mechanism can be cleaned or replaced. In the process of boring, cleaning of the steering head mechanism can create unacceptable down time. And if the steering head mechanism needs to be replaced, this creates unacceptable and unnecessary expense.
What is needed is a steering head mechanism that can be used with an earth boring machine such that the earth boring machine can be periodically reversed without causing the steering head mechanism to seize. What is also needed is such a steering head mechanism that is relatively easy and inexpensive to manufacture and which can be used in the same manner as current steering head mechanisms are used.